drm/i915: Introduce vfunc read_luts() to create hw lut

In this patch, a vfunc read_luts() is introduced to create a hw lut
i.e. lut having values read from gamma/degamma registers which will
later be used to compare with sw lut to validate gamma/degamma lut values.

v3: -Rebase
v4: -Renamed intel_get_color_config to intel_color_get_config [Jani]
    -Wrapped get_color_config() [Jani]
v5: -Renamed intel_color_get_config() to intel_color_read_luts()
    -Renamed get_color_config to read_luts
v6: -Renamed intel_color_read_luts() back to intel_color_get_config()
     [Jani and Ville]
Signed-off-by: Swati Sharma <swati2.sharma@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1559123462-7343-2-git-send-email-swati2.sharma@intel.com

drivers/gpu/drm/i915/i915_drv.h

@@ -340,6 +340,7 @@ struct drm_i915_display_funcs {
 	 * involved with the same commit.
 	 */
 	void (*load_luts)(const struct intel_crtc_state *crtc_state);
+	void (*read_luts)(struct intel_crtc_state *crtc_state);
 };
 
 struct intel_csr {

drivers/gpu/drm/i915/intel_color.c

@@ -879,6 +879,14 @@ int intel_color_check(struct intel_crtc_state *crtc_state)
 	return dev_priv->display.color_check(crtc_state);
 }
 
+void intel_color_get_config(struct intel_crtc_state *crtc_state)
+{
+	struct drm_i915_private *dev_priv = to_i915(crtc_state->base.crtc->dev);
+
+	if (dev_priv->display.read_luts)
+		dev_priv->display.read_luts(crtc_state);
+}
+
 static bool need_plane_update(struct intel_plane *plane,
 			      const struct intel_crtc_state *crtc_state)
 {

drivers/gpu/drm/i915/intel_color.h

@@ -13,5 +13,6 @@ void intel_color_init(struct intel_crtc *crtc);
 int intel_color_check(struct intel_crtc_state *crtc_state);
 void intel_color_commit(const struct intel_crtc_state *crtc_state);
 void intel_color_load_luts(const struct intel_crtc_state *crtc_state);
+void intel_color_get_config(struct intel_crtc_state *crtc_state);
 
 #endif /* __INTEL_COLOR_H__ */